Red Seal Gasfitter — Class B Practice Exam

Which method is recommended for removing air from newly installed gas lines?

1. Purging the lines with gas

2. Flushing with water

3. Using a vacuum pump

4. Waiting for natural gas absorption

The correct answer is: Purging the lines with gas

The recommended method for removing air from newly installed gas lines is to purge the lines with gas. This process involves introducing natural gas into the system, which pushes out the air and any other gases present. By doing so, it helps to ensure that the gas line is filled with the correct combustible gas and reduces the risk of explosion or other hazards associated with the presence of air in the line. Purging not only removes air but also ensures that the gas line is ready for operation by properly pressurizing it with the fuel it is intended to carry. It's an essential safety step since air mixed with natural gas can create an explosive mixture. The other methods listed are not suitable for this specific purpose. Flushing with water could lead to corrosion and other problems in the gas lines, while using a vacuum pump does not effectively introduce the gas needed to ensure safe operations. Waiting for natural gas absorption is impractical, as it would take a considerably long time and would not guarantee effective removal of air from the system.